Infrared nonlinear optical crystal materials have a promising future in the field of civil use, scientific research and military, such as molecular spectrum, non-invasive medical diagnostic test, environmental monitoring, deep space exploration, space telescope, infrared laser radar, laser communication, opto-electronic countermeasure, and the like. At present, mid-/far-infrared laser with wavelength of 2˜20 μm is obtained based on the principles of nonlinear optics and infrared nonlinear optical frequency conversion technology. Commercial mid-/far-infrared nonlinear optical crystals mainly contain AgGaS2, AgGaSe2, ZnGeP2, and the like. These crystals have been widely used in production, live, scientific research and military equipment, while these crystals have respective shortcomings, such as low laser damage threshold, difficult growth of large crystal, and their comprehensive performance could not meet increasing application demands.
With development of technology and increasing demands, it is of great significance and urgent to develop more infrared nonlinear optical crystals with more outstanding comprehensive performance. Therefore, the development and growth of new infrared nonlinear optical crystals is not only a challenge for the synthesis and growth of crystal materials, but has important strategic significance in development of civilian high-tech industry and strengthening of national defense capability.